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Date: Wed, 21 Nov 2012 08:32:26 -0500
From: Dave Angel <d@davea.name>
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To: inshu chauhan <insideshoes@gmail.com>
Subject: Re: Index Error
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> 
> <snip>
> 
>>
>> Back to an earlier comment.  I asked if N was ever bigger than x or
>> bigger than y, and you said never.  But your ComputeClasses will have
>> such a case the very first time around, when cx==0, cy==0, and
>> ring_number == 1.
>>
> 
> I doubt this , M confused..
> 

I'll paste an excerpt of the last source I've seen from you:

"""

def GenerateRing(x,y, N): Generates square rings around a point in data
which has 300 columns(x) and 3000 rows(y)
    indices = []
    for i in xrange(-N, N):
        indices.append((x+i, y-N))
        indices.append((x+N, y+i))
        indices.append((x-i, y+N))
        indices.append((x-N, y-i))
    return indices


def ComputeClasses(data):
    radius = .5
    points = []
    for cy in xrange(0, data.height):
        for cx in xrange(0, data.width):

            if data[cy,cx] == (0.0,0.0,0.0):
                continue
            else :
                centre = data[cy, cx]
                points.append(centre)


            change = True

            while change:

                for ring_number in xrange(1, 100):
                    change = False
                    new_indices = GenerateRing(cx, cy, ring_number)
"""

When that GenerateRing() is first called, cy will be zero, cx the same,
and ring_number will be 1.

So some of the tuples in the returned list will have negative ints.  You
don't check for that either.

I still think that data.height and data.width aren't the right limits to
be using.

-- 

DaveA